The terms used below, such as front and back, or front and rear, relate to the firing direction, with the front pointing in the firing direction, the back pointing away from the firing direction. Where proximal or distal are used to explain a feature, proximal will refer to herein as the back and the distal will refer to herein as the front.
To set the stage for developing improved suppressors, it is necessary first to identify the critical elements of the attendant flow fields as thoroughly documented in Klingenberg, Firearmter and Heimerl, Joseph M., Firearm Muzzle Blast and Flash, AIAA Progress in Astronautics and Aeronautics, Volume 139, 1992.
These characteristics can be broken down into three core elements. The first two core elements are: the precursor blast; and a main blast set up by the expanding gases. The precursor blast consists of mostly air with a small amount of propellant and the main blast is made up of spherical pressure waves that quickly overtake the fired projectile. Both of these blasts are sources of low frequency noise that carry very far distances. The third core element is the highly visible gas flash which follows the blast.
In general, a gas flash occurs because air mixes with the fuel rich propellants and the high temperatures from the blast waves. The result of this mixture forms a gas flash which is greatly increased in the secondary flow region that occurs away from the muzzle of a firearm.
When a gas flash forms, it occurs in three parts: primary, intermediate, and secondary flashes. The primary flash forms at the muzzle in the supersonic flow region and is very small. An intermediate flash occurs directly behind the projectile, but in front of the Mach disk leading any supersonic flow region. (Not all firearms have supersonic discharge flows.) The secondary flash is the most severe, and it occurs downstream of the firearm muzzle, and after the normal shock resulting from the muzzle gas over-expansion. The large flash seen when firing a projectile is actually the secondary flash.
With an understanding of the three core elements involved in the blast and flash from a projectile, the individual components can be analyzed to assess their critical components.
Traditionally, suppressors (also referred to as silencers) have been built with an outer tube and internal baffling components. The outer tube is steel or aluminum tubing and has end caps, either welded or threaded in place. The internal components are typically a set of flat disks each having a hole through the center thereof with spacers therebetween to create a volume of space (referred to as a baffle chamber) between each set of disks. Improvements on the flat spacer configuration include various expansion cone shape baffles that are either machined or stamped. Some of these baffles include holes at various places to re-direct gases and increase turbulence of the gases internally as the bullet passes thought the baffles. Such a configuration aids in reducing the noise produced by the firearm.
The pieces of the outer tube attach in a gas-tight manner onto, for example, an outside thread on the muzzle of a rifle. The disks extend in a plane that is orthogonal to the firing axis of the barrel. The firing opening of the disks can taper outward towards the front.
More modern suppressors that make use of what are referred to as “M” and “K” baffles incorporate both the expansion cone concept with the spacer as a single unit. These units are individually machined on a Computer Numerical Control (CNC) lathe and stacked on top of one another and are subject to stack-up tolerances during assembly. Recent designs include a monolithic baffle that is either drilled or milled from a round piece of stock. For example, U.S. Pat. Nos. 6,079,311 and 6,302,009 to O'Quinn et al. describe a monolithic baffle drilled or milled from a round piece of stock.
Characteristics of designing a suppressor include the number and the shape of the chamber parts. Each silencer also must be adapted to the weapon and to the ammunition used in the weapon. Another aspect to consider in this context is the silencer's sound-reducing requirements. Each chamber part reduces the muzzle report by a given amount and, therefore, a larger number of chambers is desirable. However, because the silencer increases the total length of the firearm and adds weight to the muzzle (thus impairing the weapon's balance), overall, the silencer should be as short and light as possible.
Considering the principal characteristics of the blast wave, studies have found that it is essentially a spherical blast wave that travels rapidly but also decays rapidly both strength-wise and time/distance-wise. Relative to the flow-field attendant to the flash, it establishes after or behind the main blast wave with a structure very similar to that of a traditional under-expanded jet plume often seen in propulsion applications. The key elements of the post-blast wave flow field are the free jet boundary and the highly under-expanded jet flow region all flowing strongly in the downstream axial direction. The over-expanded gas results in the normal shock or Mach disk, which causes the secondary flash and a significant portion of the noise. The important point is that the key physics of this type of flow structure is common in propulsion aerodynamics, and can be used to generate performance correlations for use in developing more efficient suppressor designs.
There are a wide range of firearm suppressor designs. All current designs apparently have three recurrent features: 1.) a circular or near circular cross-section with a diameter approximately five times the firearm's muzzle diameter; 2.) a solid outer surface so no gases can enter or escape the suppressor except through its entrance and exit ports; and 3.) complex flow nozzles, baffles and/or chambers interior to the suppressor for capturing the muzzle gases and mitigating the blast over-pressure level.
U.S. Pat. No. 2,363,563 relates to an air-cooled gun barrel and discloses a cooling device that is applied to the end of a usual jacket cylinder of a barrel of an automatic (rapid) firing weapon. The cooling device comprises a short sleeve in the interior of which three ring members are arranged and secured to the inside surface of the sleeve by radial fins. The three rings are specifically arranged in the annular space between sleeve and the central bullet passage way. These rings are—in the longitudinal direction—first diverging and thereafter converging.
The ring members acting as aspirating rings confine the expansion of an expanding flame sheet issued from the barrel muzzle and create suction at and beyond the gun muzzle which causes a flow of air along the barrel, the air entering the annular space between the barrel and the jacket through airports.
Thus, the device disclosed in U.S. Pat. No. 2,363,563 is provided to cause airflow within the annular space between the gun barrel and the jacket cylinder so as to cool the gun barrel of an automatic rapid firing weapon.
U.S. Pat. No. 1,860,276 is concerned with a firearm and discloses a firearm suppressor comprising a sleeve that is fixed on the outside of the gun in any convenient manner as for instance by screwing.
Accordingly, it is a primary objective of the present invention to provide a firearm suppressor that employs advanced fluid dynamic principles to consistently deliver levels of noise and flash suppression equal to or better than current suppressors.
It is another primary objective to provide an improved firearm suppressor with significantly increased useful life span over that of current firearm suppressors.
It is another primary objective to provide an improved firearm suppressor technology to control the muzzle blast wave and overexpansion flow for better suppression.
It is another objective, commensurate with the above-listed objects, to provide an improved suppressor which is durable and safe to use.
A further objective is to provide a firearms suppressor having means to evacuate the suppressor chamber of fluids such as water for use after immersion in a fluid.